Cultural influence on the effects of attitudes, subjective norms, and perceived behavioural control (PBC) on behavioural intentions can vary with types of behaviours. The current study compared American and Korean undergraduates for the effects of each of the Theory of Planned Behaviour components on intentions to sign an organ donor registry and to have family discussion about organ donation. For intentions to sign, results showed that attitudes were a stronger predictor among Americans than Koreans and that PBC was a significant predictor only among Koreans. While attitudes and subjective norms were similarly related to Americans' intentions to sign, subjective norms were more strongly related to Koreans' intentions to sign than attitudes and PBC. For intentions to have family discussion, Americans considered subjective norms to a greater extent than Koreans did. While subjective norms and PBC were more important than attitudes were among Americans, PBC was more important than subjective norms and attitudes among Koreans. Theoretical and practical implications of these and other findings are discussed.